What happened
The pilot reported that this flight was the first operation following an engine overhaul. During the takeoff climb phase, the aircraft reached an altitude of approximately 500 feet when the engine suddenly lost power. Unable to maintain altitude or return to the runway, the pilot executed a forced landing on the ground adjacent to the runway.
The investigation
A post-accident examination of the engine revealed a critical maintenance error. The exhaust rocker arm adjusting mechanism had not been torqued to the required specification of 450 inch-pounds. This lack of proper torque allowed excessive cylinder pressure to develop during operation, which ultimately bent the intake pushrod, leading to the loss of engine power.
Findings
The primary factor contributing to this accident was the failure to properly torque the exhaust rocker arm adjusting mechanism during the prior engine overhaul. This maintenance oversight resulted in mechanical interference within the engine, specifically the bending of the intake pushrod due to excessive pressure.